1. Field of the Invention
The invention relates to random access optical discs, and in particular, to an efficient method for data recording and data verification of an optical disc.
2. Description of the Related Art
FIG. 1 is a simplified block diagram showing an optical disc drive 120 coupled to a host 110. The optical disc drive 120 performs random read and recording operations on an optical disc such as a Blue-Ray rewritable disc, a DVD-RAM disc or other rewritable discs (not shown). To record data, the host 110 may issue write commands #WC designated to record one or more data blocks #WD into corresponding destination addresses of the optical disc. The optical disc drive 120 typically comprises a processor 122, a buffer 124 and a drive unit 126. The drive unit 126 comprises a mechanical unit including a rotation motor, a pickup head and servo control loop circuits (not shown) for physical access of the optical disc. The buffer 124 is a memory device buffering input and output data passing between the host 110 and drive unit 126. The processor 122 is a processing unit providing control of the optical disc drive 120 according to preinstalled firmware (not shown), and manages the buffer 124. The architecture is common for those skilled in the art, as such detailed description is not given herein.
FIG. 2 is a flowchart of a conventional random access control method. Random access of optical discs is a basic function, comparing to conventional sequential access, whereby various requests may be randomly issued by the host 110 to elastically access the optical disc, such as reading, recording, and erasure of one or more data blocks. Conventionally, a recording operation is followed by a verification operation. In step 202, the optical disc drive 120 enters a waiting loop to await any commands delivered from the host 110. In step 204, the optical disc drive 120 receives a write command #WC requesting to record a data block #WD to a destination address on the optical disc. The associated data block #WD may also be provided by the host 110 and buffered in the buffer 124. In step 206, the processor 122 instructs the drive unit 126 to perform a track seeking operation, moving the pickup head on to the destination address. In step 208, upon pickup head arrival at the destination address, the data block #WD buffered in the buffer 124 is converted into a radiation form and recorded onto the optical disc by the drive unit 126. In step 210, the recorded data block #WD on the destination address is further verified to ensure data integrity. A conventional data verification process may comprise of consecutive mechanical operations. For example, to verify the recorded data block #WD, a reading process may be required over the same destination address. To accomplish the reading process, another track seeking step may also be required. Error detection and correction such as Reed Solomon ECC algorithm may be performed on the readouts. Besides ECC correction, the readouts may also be compared with the original data block #WD stored in the buffer 124 to determine their identity. In step 212, the verification result is output, indicating whether an erroneous recorded data block #WD is found. If so, an error handling procedure is triggered in step 214, requesting a rerecording process, a correction process or else. Otherwise, the process returns to step 202, entering the waiting loop to await any other commands.
Conventionally, a track seeking process needs a time consuming mechanical movement involving motion of pickup heads and servo controls. The steps in FIG. 2 form a subroutine cycle triggered every time a write command #WC is issued, in which at least one track seeking and data verification is required per cycle. When a number of random write/read commands are issued, each bound to various addresses without order and continuity, the optical disc drive performance will significantly decrease due to the inefficiency of track seeking. Thus, an enhanced method to reduce unnecessary track seeking is desirable.